1. Field of the Invention
The invention relates to a hybrid vehicle equipped with an engine and an electric motor/generator as propulsion power sources, and to a control method for the hybrid vehicle.
2. Description of Related Art
There is known a control apparatus that is applied to a hybrid vehicle capable of locking an electric motor/generator connected to a power splitting mechanism and that locks the electric motor/generator to restrain rises in the temperature of the electric motor/generator if the temperature of the electric motor/generator is higher than a predetermined criterion temperature (Japanese Patent Application Publication No. 2002-271911 (JP 2002-271911 A)).
In recent years, cylinder deactivation engines capable of deactivating one or more of a plurality of cylinders so as to improve the engine fuel economy have been developed. However, application of such a cylinder deactivation engine as an engine of a hybrid vehicle that is capable of locking an electric motor/generator has not been fully considered. In the control apparatus of JP 2002-271911 A, a temperature condition for locking an electric motor/generator is set merely on the assumption that the electric motor/generator is mounted in a hybrid vehicle equipped with an ordinary engine. Therefore, in the case where the control apparatus of JP 2002-271911 A is immediately applied to a hybrid vehicle equipped with a cylinder deactivation engine so that, with regard to the locking of the electric motor/generator, the same criterion is set for both the reduced-cylinder operation and the all-cylinder operation, a problem may possibility occur.